[merged mm-stable] mm-page_idle-handle-device-exclusive-entries-correctly-in-page_idle_clear_pte_refs_one.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: mm/page_idle: handle device-exclusive entries correctly in page_idle_clear_pte_refs_one()
has been removed from the -mm tree.  Its filename was
     mm-page_idle-handle-device-exclusive-entries-correctly-in-page_idle_clear_pte_refs_one.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/page_idle: handle device-exclusive entries correctly in page_idle_clear_pte_refs_one()
Date: Mon, 10 Feb 2025 20:37:55 +0100

Ever since commit b756a3b5e7ea ("mm: device exclusive memory access") we
can return with a device-exclusive entry from page_vma_mapped_walk().

page_idle_clear_pte_refs_one() is not prepared for that, so let's teach it
what to do with these PFN swap PTEs.  Note that device-private entries are
so far not applicable on that path, as page_idle_get_folio() filters out
non-lru folios.

Should we just skip PFN swap PTEs completely?  Possible, but it seems
straight forward to just handle them correctly.

Note that we could currently only run into this case with device-exclusive
entries on THPs.  We still adjust the mapcount on conversion to
device-exclusive; this makes the rmap walk abort early for small folios,
because we'll always have !folio_mapped() with a single device-exclusive
entry.  We'll adjust the mapcount logic once all page_vma_mapped_walk()
users can properly handle device-exclusive entries.

Link: https://lkml.kernel.org/r/20250210193801.781278-14-david@redhat.com
Fixes: b756a3b5e7ea ("mm: device exclusive memory access")
Signed-off-by: David Hildenbrand <david@redhat.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lyude <lyude@redhat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yanteng Si <si.yanteng@linux.dev>
Cc: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_idle.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/mm/page_idle.c~mm-page_idle-handle-device-exclusive-entries-correctly-in-page_idle_clear_pte_refs_one
+++ a/mm/page_idle.c
@@ -62,9 +62,14 @@ static bool page_idle_clear_pte_refs_one
 			/*
 			 * For PTE-mapped THP, one sub page is referenced,
 			 * the whole THP is referenced.
+			 *
+			 * PFN swap PTEs, such as device-exclusive ones, that
+			 * actually map pages are "old" from a CPU perspective.
+			 * The MMU notifier takes care of any device aspects.
 			 */
-			if (ptep_clear_young_notify(vma, addr, pvmw.pte))
-				referenced = true;
+			if (likely(pte_present(ptep_get(pvmw.pte))))
+				referenced |= ptep_test_and_clear_young(vma, addr, pvmw.pte);
+			referenced |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
 		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 			if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
 				referenced = true;
_

Patches currently in -mm which might be from david@redhat.com are

mm-factor-out-large-folio-handling-from-folio_order-into-folio_large_order.patch
mm-factor-out-large-folio-handling-from-folio_nr_pages-into-folio_large_nr_pages.patch
mm-let-_folio_nr_pages-overlay-memcg_data-in-first-tail-page.patch
mm-let-_folio_nr_pages-overlay-memcg_data-in-first-tail-page-fix.patch
mm-move-hugetlb-specific-things-in-folio-to-page.patch
mm-move-_pincount-in-folio-to-page-on-32bit.patch
mm-move-_entire_mapcount-in-folio-to-page-on-32bit.patch
mm-rmap-pass-dst_vma-to-folio_dup_file_rmap_pte-and-friends.patch
mm-rmap-pass-vma-to-__folio_add_rmap.patch
mm-rmap-abstract-large-mapcount-operations-for-large-folios-hugetlb.patch
bit_spinlock-__always_inline-unlock-functions.patch
mm-rmap-use-folio_large_nr_pages-in-add-remove-functions.patch
mm-rmap-basic-mm-owner-tracking-for-large-folios-hugetlb.patch
mm-copy-on-write-cow-reuse-support-for-pte-mapped-thp.patch
mm-convert-folio_likely_mapped_shared-to-folio_maybe_mapped_shared.patch
mm-config_no_page_mapcount-to-prepare-for-not-maintain-per-page-mapcounts-in-large-folios.patch
fs-proc-page-remove-per-page-mapcount-dependency-for-proc-kpagecount-config_no_page_mapcount.patch
fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount.patch
fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-mapmax-config_no_page_mapcount.patch
fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-smaps-smaps_rollup-config_no_page_mapcount.patch
mm-stop-maintaining-the-per-page-mapcount-of-large-folios-config_no_page_mapcount.patch